2020-21 KTM 390 Adventure Bike Build
Above is a 2020 KTM 390 Adventure. After buying it and riding it stock, down the roads and out in the dirt and the bumps, I can honestly say it's a big dumb pig pig. Slow and heavy. Totally reminds me of buying the first Honda CRF 250 L, that came into Arizona, and developing it.
When I rode the 250L, outside of the dealership, I wanted to ask them to take it back and see if I could have my money back. Thing was, I bought it because a great price point at $5000 or whatever it was then. I also knew, that after I figured out the performance kit for it, that it would be totally different. And it worked. That bike weighed 300 lbs and had 18 hp stock. We got some weight off and got the power to 26 and it was a whole new bike. Honda sold a bunch of bikes and we sold a bunch of kits.
This new 390 KTM is the same kind of thing. It's on the heavy side, but some weight can come off. It feels odd and wrong, as far as ergonomics go. Especially for control in the dirt. But that can be fixed. And finally it needs more power, get up and go and some reliability. And we can definitely fix that.
As we started taking apart this bike, we realized how heavy the battery was. For about $100, you can loose a whole 6 lbs by going to a good lithium battery. This is high centered weight you feel. It's a must do
The people who design the best performance products ( us and just a few others ) know darn well to take measurements of stock componets first. On a fuel injected bike, the fuel pressure is so, so critical to performance and even maintaining stock running condition. The running pressure of the stock bike is 54 psi. If the pressure falls below this, then starting and acceleration will suffer. The lower it goes, the worse performance gets.
The next big parameter, that's super critical to know, on a fuel injected bike, is the air / fuel ratio. Now on this particular bike, it has an Oxygen sensor welded in the head pipe to make what we call a "closed loop" injection system. This means that the O2 sensor feeds back information to the ECU ( electronic control unit ). This means that the system tries to make adjustments to the fuel amount to the injector, so that the pre determined air/ fuel ratio is kept.
In the case of this bike, the pre determined air/ fuel ratio, seems to be 14.7 :1. That's what the gauge we hooked up to shows. When you ride down the street, the gauge fluctuates a bit, but it centers around 14.7.
When you crack the gas, there is a bit of an accelerator pump kick in, but not a lot. It shoots to 13.5 :1, which is a bit richer to aid in the "get up and go", but then goes right back to 14.7.
This is important to know. Because we need to know how far you can go with opening up exhaust and intake flow, before the ecu can't adjust anymore and the bike starts to lean out.
Now that a few parameters and notes, on how it's running are taken, lets go ride it. The first thing you may notice, is that it's an odd feeling bike, when you are riding it. Especially offroad.
You'll definitley want to remove the rubber inserts from the footpegs. That done by removing the bolt under the bottom of the peg. Then at least you feet will be in a better position for using the foot controls.
After that, you'll really be in a better riding position if you use these bar risers we have, to get the bars up higer and further back. You can see the black piece sitting on the tank above, which is the bar riser we have for use with the stock handlebars. These move the stock bars up 3/4" or 19mm and back 1.25" or 30mm. For a small amount of money, this is a HUGE difference in comfort and control
Some people will prefer to use a more comfortable feel for offroad, like the straighter bend MX bar they may be use to. Those bars are normally a 1-1/8" diameter, instead of the stock 1". They are also a lower height, that the stock bar height.
To get MX bars to the area that they need to be, You'll want to use both of these clamps here.
( image coming soon )
After the fixing of the handlebar posistion and taking the rubbers off the foot pegs. The feeling of the seat and other sizing changes are a personal preference.
We will be making some components that are better and more adjustable than stock, in the near future.
So for now this paragraph is a place holder
Now let's get back to the best stuff, which is making and improving power delivery. You can see a dyno run of our bike in stock condition below. It's the lower of the 2 lines on both of the graphs. This is on the stock tires at 25 psi.
The upper line, is just the addition of our end cap. There is NO reason to spend over $100 to make this muffler good. Our end cap makes the stock muffler make as much power as any of the expensive aftermarket mufflers. We know, we tried those too
So you can see our high flowing endcap with it's 1.5" outlet hole, versus the stock 7/8" hole, which is also confined for a length of 4". That's a lot of restriction. The stock muffler has a straight through 1 7/8" core, so with the new end cap, you can easily understand how any high dollar muffler, isn't going to breath any better than this.
You just drill out the stock rivets and remove the stock cap. Then install ours with the supplied torx screws.
And it's the only exhaust on the market, including the stock one, that can use an optional spark arrestor. These bikes go in the brush and trees in the offroad areas too, so why no one want's to help keep you from lighting your area on fire, is just mind boggling.
Above you see the improvement of adding a new ECU from Coober, and thier free flowing air box cover. It's the orange line, that is the most power now, all the way up and another 1000 rpm out. Even though it doesn't make anymore peak power, look how much more power it makes all the way up and the new redline.
Definitley a fun improvement over just the end cap. This still uses the stock header, with the double catalytic converters.
The last stage in making easy power on the 390, is removing the stock header, with it's 2 catalytic converters, and replacing it with our normal style header. It has no cats and ofcourse is much free-er flowing than the stock one.
It weighs about 5 lbs less than the the stock header, is extremely tough against getting bent, and ofcourse runs cooler than the stock one.
Most importantly, it's a nice gain in power and more importantly torque, over the stock header.
You have to use the Coober ecu to use this header, as the bike will run far to lean with the stock ecu and this. The coober ecu has 2 maps in it, and switches to the De-Cat map, when it senses the leaner running of this header.
The bike will be louder with this header, since the stock cats do suppress sound, when they are suppressing air flow.
With our end cap and new header, and the Coober ecu, you can see the impressive 3 hp and 3 ft-lb gain in torque, above. The best part is, the big gain in torque, starts from 2500 rpm and continues. It's rare something gains this big right away. This is what makes it so much more rideable and fun. Plus being able to pull another 1000 rpm is really nice.
Most people will stop here. If you need more acceleration, then we need to change gearing.